My work focuses on understanding anthropogenic changes in precipitation and atmospheric circulation by employing climate models of varying levels of complexity. This thesis has two goals: (1) to understand the forced response of tropical air-sea interactions across time scales and their extratropical impact, and (2) to explore reasons underlying model uncertainties in simulating tropical and extratropical climate. My dissertation comprises four individual projects. My first project explored the mechanism of how the Walker circulation (WC) responds to CO2 across time scales. The prevailing consensus suggests that the long-term weakening of the WC is primarily driven by greenhouse gas-induced sea surface temperature (SST) warming, while the fast response of the WC is independent of changes in SST. However, my findings indicate that the air-sea interactions play a substantial role during fast response period. By analyzing data from Coupled Model Intercomparison Project (CMIP) Phase 5 under abrupt4xCO2 scenarios, models with stronger air-sea coupling in the equatorial Pacific simulate an initial strengthening of the WC, which contrasts with the long-term response. Conversely, models with weaker air-sea coupling simulate a monotonically weakening of the WC. My results suggest that the inter-model discrepancy in the WC changes originate from the fast component. My second project found that the uncertainties in the future projection of the summer North Pacific subtropical high (NPSH) stem from both inter-model SST-driven and non-inter-model SST-driven uncertainties in tropical precipitation. I further explored the link between tropical precipitation and the NPSH by modifying the diabatic heating in both a stationary baroclinic model and a comprehensive climate model. Building upon the first two chapters, my third project investigated the interplay between the tropical air-sea interaction and the summer NPSH under anthropogenic warming. I found that the inter-model spread in projecting the fast WC changes contributes to the variability in the NPSH responses among models. Specifically, models with a stronger tropical equatorial Pacific air-sea coupling exhibit a strengthening of the WC and central Pacific cooling, producing anomalous tropical precipitation that further modulates the NPSH via the Gill response. During the collaboration with my advisor on the fourth project, we found considerable inter-basin variations in the future projection of the tropical hydrological sensitivity (HS) regardless of how SST warms. I further demonstrated the remote impact of the inter-basin discrepancy in HS on land precipitation and surface temperature by exploring corresponding tropical-extratropical atmospheric teleconnections.